1. Field of the Invention
The present invention relates to D.C. motors, and, more specifically, to an improvement in an armature shaft and a commutator of a D.C. motor.
2. Description of the Prior Art
FIG. 1 shows a main part of a conventional D.C. motor. In this figure, a plurality of narrow parallel channels are formed longitudinally around the intermediate portion 1 of a shaft 2 made of iron. The shaft 2 is pressed into the central aperture of an armature core 3 to fixedly mount the armature core 3 to the channel-formed portion 1 of the shaft 2. Adjacent the portion 1, a commutator 4 is also rigidly mounted to the shaft 2. A gear 5 is formed at one end of the shaft opposite the commutator 4 with respect to the armature core 3.
The commutator 4 comprises a hollow cylinder 4a made of an insulating material such as resin, a plurality of conductive segments 4b flush-mounted on the outer surface of the cylinder 4a at equal intervals, and an insert 4c provided on the inner surface of the hollow cylinder 4a. The cylinder 4a, segments 4b and insert 4c are integrally molded to form the commutator 4. The conductive segments 4b are connected to corresponding taps of armature coils 6 wound around the armature core 3.
As described, the commutator 4 of the conventional D.C. motor needs the insert 4c which is integrally formed inside the hollow cylinder 4a made of resin, and it is necessary to press the shaft 3 into the commutator 4. Accordingly, the conventional D.C. motor has many elements and assembly work thus involves many steps. Moreover, since the commutator 4 is fixed to the shaft 3 by way of pressing the shaft 3 into the commutator 4, it sometimes happens that the shaft 3 is pressed into the commutator 3 in such a manner that the control axis of the shaft 3 and that of the commutator 4 are offset from each other.